Three electrode arc-discharge lamp

Abstract

A method of operating an arc discharge lamp that has first and second electrodes is described. First, the first electrode is heated with a third electrode with a first arc until the first electrode temperature is sufficiently elevated to allow for thermionic emission. Then, a first voltage is applied between the first and second electrode at a voltage less than 1000 volts to create a second arc.

1. An arc discharge lamp, comprising:
 an assembly enclosing an ionizable medium; 
 a first, second, and third electrodes sealed within the assembly, the first electrode separated from the second electrode by a first distance, the first electrode separated from the third electrode by a second distance less than the first distance; 
 a ballast circuit configured to use the first electrode as an anode and the third anode as a cathode to initiate a first arc at a first voltage, and configured to use the first electrode as a cathode and the second electrode as an anode to initiate a second arc with a second voltage after the first arc is initiated, wherein the second voltage is less than 1000 volts and the first voltage is less than 10,000 volts; and 
 a temperature sensor thermally coupled to the first electrode and wherein the second voltage is not applied until the temperature sensor detects a predetermined temperature of the first electrode. 
 
   
   
     2. The arc discharge lamp of  claim 1 , wherein the second electrode is electrically coupled to the third electrode. 
   
   
     3. The arc discharge lamp of  claim 1 , wherein the first electrode is formed of a multi-component structure wherein a work-function between the first electrode and the third electrode is different than the work function between the first electrode and the second electrode. 
   
   
     4. The arc discharge lamp of  claim 1 , wherein the first voltage is less than one-half a fourth voltage, wherein the fourth voltage is an amount of voltage to initiate an arc between the first electrode and the second electrode if the third electrode is not used. 
   
   
     5. An arc discharge lamp, comprising:
 an assembly enclosing an ionizable medium; 
 a first, second, and third electrodes sealed within the assembly, the first electrode separated from the second electrode by a first distance, the first electrode separated from the third electrode by a second distance less than the first distance; and 
 
     a ballast circuit configured to use the first electrode as an anode and the third anode as a cathode to initiate a first arc at a first voltage, and configured to use the first electrode as a cathode and the second electrode as an anode to initiate a second arc with a second voltage after the first arc is initiated, wherein the second voltage is less than 1000 volts and the first voltage is less than 10,000 volts wherein the ballast circuit further includes an ignition transformer connected to the third electrode and wherein a current required to maintain the arc between the first electrode and the second electrode does not flow in the ignition transformer. 
   
   
     6. An arc discharge lamp, comprising:
 an assembly enclosing an ionizable medium; 
 a first, second, and third electrodes sealed within the assembly, the first electrode separated from the second electrode by a first distance, the first electrode separated from the third electrode by a second distance less than the first distance and wherein the first electrode has an aft portion and a tip portion and is suspended bV Vogel mount members and the third electrode is positioned near the aft portion of the first member; and 
 a ballast circuit configured to use the first electrode as an anode and the third anode as a cathode to initiate a first arc at a first voltage, and configured to bombard electrons from the third electrode to the first electrode causing the first electrode to heat until a second arc is initiated at a second voltage between the first electrode and the second electrode. 
 
   
   
     7. The arc discharge lamp of  claim 6 , wherein the second electrode is electrically coupled to the third electrode. 
   
   
     8. The arc discharge lamp of  claim 6 , the first electrode is formed of a multi-component structure wherein a work-function between the first electrode and the third electrode is different than the work function between the first electrode and the second electrode. 
   
   
     9. The arc discharge lamp of  claim 6 , wherein the first voltage is less than one-half a fourth voltage, wherein the fourth voltage is the amount of voltage to initiate an arc between the first electrode and the second electrode if the third electrode is not used. 
   
   
     10. An arc discharge lamp, comprising:
 an assembly enclosing an ionizable medium; 
 a first, second, and third electrodes sealed within the assembly, the first electrode separated from the second electrode by a first distance, the first electrode separated from the third electrode by a second distance less than the first distance; and 
 a ballast circuit configured to use the first electrode as an anode and the third anode as a cathode to initiate a first arc at a first voltage, and configured to bombard electrons from the third electrode to the first electrode causing the first electrode to heat until a second arc is initiated at a second voltage between the first electrode and the second electrode and wherein the ballast circuit further includes an ignition transformer connected to the third electrode and wherein a current required to maintain the arc between the first electrode and the second electrode does not flow in the ignition transformer. 
 
   
   
     11. A method of operating an arc discharge lamp having first and second electrodes, comprising:
 heating the first electrode with a third electrode with a first arc until the first electrode temperature is sufficiently elevated to allow for thermionic emission; and 
 applying a first voltage between the first and second electrode at a voltage less than 1000 volts to create a second arc; 
 wherein heating the first electrode includes a first circuit having a first current, and wherein the applying of a first voltage between the first and second electrode includes supplying a second current and wherein the second current does not flow within the first current. 
 
   
   
     12. The method of  claim 11 , wherein the first arc is initiated with a second voltage that is less than 1000 volts. 
   
   
     13. The method of  claim 11 , wherein the heating of the first electrode occurs due to electrons flowing from the third electrode to the first electrode. 
   
   
     14. The method of  claim 11 , wherein the creation of the second arc occurs from electrons flowing from the first electrode to the second electrode. 
   
   
     15. The method of  claim 11 , wherein the first electrode and second electrode are separated by a first distance, and the first electrode and the third electrode are separated by a second distance less than the first distance. 
   
   
     16. The method of  claim 11 , wherein heating the first electrode includes a second circuit having a second current, and wherein the method further includes sensing the second current for a predetermined level before the applying of the first voltage between the first and second electrode. 
   
   
     17. The method of  claim 11 , further comprising stopping the first arc after the second arc has been initiated.